U.S. Pat. No. 4,598,556, which is assigned to the Assignee of the present invention, discloses a high efficiency refrigeration system in which a non-azeotropic binary refrigerant is used. The disclosed system has a multiple stage compressor. Multiple heat exchangers are provided in series with the refrigeration output from the condenser for cooling the refrigerant prior to expansion by the evaporator.
An article entitled "A New Technology in Energy-Efficient Electrically Driven Aircraft Environmental Control Systems" authored by W. Cloud, J. McNamara and David B. Wigmore, presented at the 21st IECEC Conference, Aug. 25-29, 1986, discloses a vapor cycle cooling system for airframes having a multiple stage compressor with multiple subcoolers for controlling the temperature of a non-azeotropic binary refrigerant. The disclosed system does not suggest that the refrigerant may be to support the hydrodynamic bearings.
U.S. Pat. No. 4,809,521, which is assigned to the Assignee of the present invention, discloses a high efficiency cooling system utilizing non-azeotropic binary refrigerant fluid having a single stage compressor. A plurality of heat exchangers are coupled between the output of the condenser and the evaporator for cooling the refrigerant prior to expansion by the evaporator.
U.S. Pat. No. 3,221,984 discloses an oil supply system for a compressor in a refrigeration system. The oil supply system provides pressurized oil to the bearings of the compressor after the compressor motor is deenergized while the compressor is still rotating at high speed. The rotational inertia of the compressor applies pressurized gas from the compressor to an oil tank above the oil level which forces oil to flow to the bearings of the compressor for a period sufficient for the compressor to stop rotating.
Refrigeration systems utilize a mixture of refrigerant and oil to lubricate the compressor and other parts in the system. After a system is first charged there is no convenient way to directly determine the amount of oil contained in the system since the oil, unlike the refrigerant, does not evaporate from the system. Having substantial oil in a refrigeration system above an amount which is carried by the refrigerant charge could interfere with the operational efficiency of the system.